How to calculate the size of the blockchain?

I want to find the size of the blockchain data. I’ve been using this Linux command:

du --exclude=index /home/me/.bitcoin/blocks/

Is this the most accurate way to do it? And does dividing the result by 1024/1024 give the size of the blockchain in GBs?

Note: The --exclude=index part excludes the blocks/index/ subfolder, which I’ve heard is extra metadata used for levelDB to make it faster to search through the blockchain. I just want to know the size of the blockchain data only, so does it make sense to omit this?